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Abstract:

An object of the invention is to provide a phase object identification
device and method which can identify a phase object in a completely
different manner from conventional methods for observing or measuring a
phase object.
A phase object identification device 1 for identifying a phase object for
changing the phase of light includes a light source 2, a sample holding
means 3 for holding a phase object 31 to be identified, a holographic
recording medium 4 on which a hologram 41 formed by interference between
reference light 25 and object light 24 that is phase-modulated by a known
phase object 32 is recorded, and a light detector 5, a phase of light 21
emitted from the light source is modulated by the phase object to be
identified to generate sample light 22, the hologram of the holographic
recording medium is irradiated with the sample light, reproduced light 23
reproduced from the hologram of the holographic recording medium is
detected by the light detector.

Claims:

1. A phase object identification device for identifying a phase object for
changing the phase of light, characterized in that the phase object
identification device comprises:a light source;sample holding means for
holding a phase object to be identified;an observation optical system
comprising a sample-side objective lens for observing a phase object to
be identified, the phase object held by the sample holding means;focusing
means for changing the distance between the phase object to be identified
and the sample-side objective lens;a holographic recording medium on
which a hologram formed by interference between reference light and
object light that is phase-modulated by a phase pattern of a known phase
object is recorded; anda light detector; andan identification optical
system in which a phase of light emitted from the light source is
modulated by a phase pattern of the phase object to be identified to
generate sample light, the hologram of the holographic recording medium
is irradiated with the sample light, reproduced light reproduced from the
hologram of the holographic recording medium is detected by the light
detector, andthe sample-side objective lens of the observation optical
system is also used as a part of the identification optical system.

2. The phase object identification device according to claim 1,
characterized in that the hologram of the holographic recording medium is
irradiated with the sample light by an objective lens arranged in such a
way that a real image of the phase object to be identified is located on
an incident pupil plane.

3. The phase object identification device according to claim 1 or 2,
characterized in that multiple holograms formed from multiple known phase
objects are recorded on the holographic recording medium, andthe phase
object identification device comprises irradiated position shifting means
for shifting an position irradiated with the sample light in the
holographic recording medium.

4. The phase object identification device according to any one of claims 1
to 3, characterized in that the observation optical system comprises an
imaging lens or an eyepiece.

5. The phase object identification device according to any one of claims 1
to 4, characterized in that the sample holding means comprises sample
positioning means for shifting a phase object to be identified in a
planar direction orthogonal to the optical axis, in order to observe a
held phase object to be identified by the observation optical system.

6. The phase object identification device according to any one of claims 1
to 5, characterized in that it comprises sample conveying means for
sequentially conveying multiple phase objects to be identified to the
sample holding means.

7. The phase object identification device according to any one of claims 1
to 6, characterized in that the phase object to be identified is a
biological cell or a bacterium, and the presence or absence of a cell
nucleus in the biological cell or the bacterium is identified.

8. The phase object identification device according to any one of claims 1
to 6, characterized in that the known phase object is a specimen within
standards, and whether or not the phase object to be identified
corresponds to the standards is identified.

9. The phase object identification device according to any one of claims 1
to 8, characterized in that it comprises reference light generation means
for generating reference light,the sample holding means is able to hold a
known phase object, a phase of light emitted from the light source is
modulated by a phase pattern of the known phase object to generate object
light, the reference light generation means generates reference light,
the holographic recording medium is irradiated with the object light and
the reference light, and a hologram formed by interference between the
object light and the reference light is recorded on the holographic
recording medium.

10. The phase object identification device according to claim 9,
characterized in that the reference light generation means is an opening
formed in the sample holding means.

11. A phase object identification method for identifying a phase object
for changing the phase of light, characterized in that:a phase object to
be identified is observed by an observation optical system;the size of
the observed phase object to be identified is adjusted by changing the
distance between a sample-side objective lens of the observation optical
system and the phase object to be identified;with the observation optical
system adjusted, a phase of light emitted from a light source is
modulated by a phase pattern of a phase object to be identified to
generate sample light;a holographic recording medium, on which a hologram
formed by interference between reference light and object light that is
phase-modulated by a phase pattern of a known phase object is recorded,
is irradiated with the sample light;reproduced light reproduced from the
hologram of the holographic recording medium is detected by a light
detector; andthe phase object to be identified is identified as having a
correlation with the known phase object if the intensity of the
reproduced light detected by the light detector is greater than a
threshold value, or the phase object to be identified is identified as
having no correlation with the known phase object if the intensity of the
reproduced light is less than the threshold value.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a phase object identification
device and a method for identifying an object (hereinafter, referred to
as a "phase object") for changing the phase of light, more particularly,
relates to a phase object identification device and a method for
identifying a phase object to be identified with the use of holography,
and also relates to novel applications using the phase object
identification device and the method.

BACKGROUND ART

[0002]While the simplest approach for observing an object is an
observation by the naked eye, the naked eye is intended to detect the
change in light intensity, and thus not suitable for the observation of
an object which brings about no change in light intensity or an object
which brings about a small change in light intensity. The same applies to
common photographs and image sensors because the change in light
intensity is detected for the photographs and image sensors. For example,
biological cells, bacteria, gratings, waveguides, microscopic steps at
the surfaces of objects, structure of the same color, etc. bring about no
changes or only small changes in light intensity, and it has been thus
difficult to observe the shapes thereof. In particular, biological cells
have many clear and colorless intercellular components, and it has been
thus extremely difficult to observe the shape and intercellular
components of the biological cells.

[0003]Therefore, conventionally, biological cells are subjected to a
pretreatment for dyeing the biological cells to visualize the shapes
thereof or identify of each intercellular component depending on the
degree of dyeing. While biological cells can be visualized by dyeing, the
dyeing technique is not able to be used in some cases depending on
targets. In addition, the pretreatment for dyeing requires time for
immobilization, etc of biological cells, which is not a simple approach
for observation. Furthermore, the dyeing may cause the biological cells
to die or alter the biological cells, thereby resulting in the problems
of failure to observe the biological cells under normal conditions and
limitation to subsequent uses of the samples.

[0004]In the meanwhile, objects which bring about no changes in light
intensity even change the phase of light in response to the difference in
refractive index or the optical path difference in many cases. The
biological cells, bacteria, gratings, waveguides, microscopic steps at
the surfaces of objects, structure of the same color, etc. mentioned
above are also included in phase objects which modulate the shape of
light. In the case of such phase objects, it is possible to observe the
phase objects by a phase-contrast microscope, a differential interference
microscope, or the like converting relative phase information into
intensity. In addition, as described in Non-Patent Document 1, techniques
for measuring absolute phase information on phase objects have been also
researched and developed. In Non-Patent Document 1, the closed-loop
feedback technique is introduced into a Mach-Zehnder interferometer, and
the entire surfaces of phase objects are scanned by the phase measurement
system which is capable of measuring changes in phase in microscopic
regions of clear and colorless phase objects with a high degree of
accuracy, thereby measuring absolute phase information on the clear and
colorless phase objects.

[0006]In recent years, the discovery of an embryonic stem cell (ES cell)
has expanded the possibilities of further regenerative medical
techniques, and various types of research and development have been
actively carried out. The ES cells refer to pluripotent stem cells
established from early embryos of animals, and cells which potentially
differentiate into all cells. Moreover, the ES cells can be cultured and
proliferated while keeping the pluripotent differentiation, and intended
cells, organs, and tissues have been thus expected to be created and used
for treatments. While cell transplantation using living cells, such as
skin transplantation, bone-marrow transplantation, and organ
transplantation, has major problems such as a scarcity of donors and
rejections, the discovery of the ES cells has been showing some signs of
solving the problems.

[0007]In addition, cytoscreening has been frequently carried out in which
cells collected from a lesion and cultured are observed under a
microscope to detect abnormal cells, tumor cells, and the like, thereby
making a diagnosis of the presence or absence of a lesion or a diagnosis
of a lesion, because the cytoscreening is relatively easy to carry out
and lessens the burden on patients.

[0008]In these cell culture techniques, the presence or absence of a
nucleus has importance. More specifically, if there is no nucleus inside
a cell, no cell division will be caused, resulting in failure to create
any cells. Therefore, it has been necessary to examine the presence or
absence of a nucleus inside a cell. As described above, the observation
of dyed cells is unfit for the examination, because the observation takes
time and cause biological cells to die or alter the biological cells. In
addition, while living cells can be observed in the observation by a
phase-contrast microscope, a differential interference microscope, or the
like, which is an examination carried out by the naked eye, the accuracy
of the examination is greatly affected by the skill and experience of the
observer. The case of the measurement with the use of the phase
measurement system has the problem of investment of time for the
measurement.

[0009]An object of the invention is to provide a phase object
identification device and method which can identify a phase object in a
completely different manner from conventional methods for observing or
measuring a phase object. In addition, another object of the present
invention is to provide novel applications using the phase object
identification device and method. An object of the present invention is
to provide an examination device and an examination method for the
nucleus of the biological cell described above as one of the
applications.

Means For Solving the Problems

[0010]In order to solve the problems, a phase object identification device
for identifying a phase object for changing the phase of light according
to the present invention is characterized in that it comprises: a light
source; a sample holding means for holding a phase object to be
identified; a holographic recording medium on which a hologram formed by
interference between reference light and object light that is
phase-modulated by a known phase object is recorded; and a light
detector, a phase of light emitted from the light source is modulated by
the phase object to be identified to generate sample light, the hologram
of the holographic recording medium is irradiated with the sample light,
reproduced light reproduced from the hologram of the holographic
recording medium is detected by the light detector.

[0011]In the phase object identification device, it is preferable that the
hologram of the holographic recording medium be irradiated with the
sample light by an objective lens arranged in such a way that a real
image of the phase object to be identified is located on an incident
pupil plane.

[0012]In the phase object identification device, it is preferable that
multiple holograms formed from multiple known phase objects are recorded
on the holographic recording medium, and the phase object identification
device comprises an irradiated position shifting means for shifting a
position irradiated with the sample light in the holographic recording
medium.

[0013]In addition, it is preferable that the phase object identification
device comprise an observation optical system for observing a phase
object to be identified, which is held by the sample holding means, and
the observation optical system comprise a sample-side objective lens, and
an imaging lens or an eyepiece. Furthermore, it is preferable that the
sample holding means comprise a focusing means for shifting a phase
object to be identified in an optical axis direction or a sample
positioning means for shifting a phase object to be identified in a
planar direction orthogonal to the optical axis, in order to observe a
held phase object to be identified by the observation optical system.

[0015]In addition, in the phase object identification device, the phase
object to be identified may be a biological cell or a bacterium, and the
presence or absence of a cell nucleus in the biological cell or the
bacterium may be identified. Alternatively, the known phase object may be
a specimen within standards, and whether or not the phase object to be
identified corresponds to the standards may be identified.

[0016]In addition, it is preferable that the phase object identification
device comprise a reference light generation means for generating
reference light, the sample holding means be able to hold a known phase
object, a phase of light emitted from the light source be modulated by
the known phase object to generate object light, the reference light
generation means generate reference light, the holographic recording
medium be irradiated with the object light and the reference light, and a
hologram formed by interference between the object light and the
reference light be recorded on the holographic recording medium.
Furthermore, the reference light generation means may be an opening
formed in the sample holding means.

[0017]A phase object identification method according to the present
invention is a phase object identification method for identifying a phase
object for changing the phase of light, characterized in that: a phase of
light emitted from a light source is modulated by a phase object to be
identified to generate sample light; a holographic recording medium, on
which a hologram formed by interference between reference light and
object light that is phase-modulated by a known phase object is recorded,
is irradiated with the sample light; reproduced light reproduced from the
hologram of the holographic recording medium is detected by a light
detector; and the phase object to be identified is identified as having a
correlation with the known phase object if the intensity of the
reproduced light detected by the light detector is greater than a
threshold value, or the phase object to be identified is identified as
having no correlation with the known phase object if the intensity of the
reproduced light is less than the threshold value.

Advantageous Effects of the Invention

[0018]The phase object identification device and method according to the
present invention are essentially different in technical idea from the
prior art in which the phase modulation pattern itself of a phase object
to be identified is identified by converting the change in phase of light
caused by the phase object into the change in light intensity, and
provided to detect the correlation between a phase to be identified and a
known phase object for identifying the phase object to be identified.
Furthermore, the phase object identification device and method according
to the present invention also have a big feature in that the correlation
between a phase to be identified and a known phase object is detected by
the calculation of optical correlation with the use of holography.

[0019]The holography refers to a technique which is capable of recording
the amplitude (intensity) and phase of light, which is able to record
phase information on a known phase object directly as a hologram. More
specifically, when a recording medium is irradiated with object light
that is phase-modulated by a known phase object and reference light so as
to overlap the object light and the reference light with each other in a
hologram recording layer of the recording medium, the hologram formed by
interference between the object light and the reference light can cause a
photoreaction of a photosensitive material in the hologram recording
layer and set the hologram in the hologram recording layer.

[0020]When the thus recorded hologram on the recording medium is
irradiated with the object light that is phase-modulated by the known
phase object under the same conditions as in the case of recording, the
object light is diffracted by the hologram to generate reproduced light
corresponding to the reference light. Furthermore, even when the hologram
is irradiated with light that is phase-modulated by a phase object which
has a correlation with the known phase object, rather than by the known
phase object, under the same conditions as in the case of recording, the
hologram will characteristically interfere with the light to generate
reproduced light depending on the correlation value (the degree of
similarity). Therefore, the detection of the presence or absence of
reproduced light can identify the presence or absence of correlation
between the phase object to be identified and the known phase object.
More specifically, unless any reproduced light is reproduced from the
hologram irradiated with the sample light under the same conditions as in
the case of recording to generate any reproduced light from the hologram,
the phase object to be identified can be identified as having no
correlation with the known phase object, or if reproduced light is
generated, the phase object to be identified can be identified as having
a correlation with the known phase object. Furthermore, the detection of
the intensity of reproduced light also allows the degree of correlation
to be identified. Other advantageous effects of the phase object
identification device and method for identifying a phase object according
to the present invention will be described in the following embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021][FIG. 1] (A) a pattern diagram for explaining the basic principle
for a phase object identification device and method according to the
present invention; and (B) a pattern diagram for explaining the basic
principle for a recording device and a method.

[0022][FIG. 2] a configuration diagram schematically illustrating an
embodiment of a phase object identification device according to the
present invention which is also available as a recording device.

[0023][FIG. 3] (A) a diagram illustrating an example of a mask shape for
forming the profile of sample light; (B) a diagram illustrating an
example of a mask shape for forming the profile of object light and the
intensity pattern of reference light; and (C) a diagram illustrating an
example of an aperture shape.

[0024][FIG. 4] (A) a cross-sectional view of a sample holding means for
recording; (B) a plan view of FIG. 4(A); and (C) a cross-sectional view
of a sample holding means for identification.

[0030]While embodiments of the present invention will be described below
with reference to the drawings, the present invention is not to be
considered limited to the following examples. FIG. 1(A) is a pattern
diagram for explaining the basic principle for a phase object
identification device and method according to the present invention. In
FIG. 1(A), a phase object identification device 1 includes a light source
2, a sample holding means 3 in which a phase object 31 (hereinafter, also
referred to as a sample) to be identified is held, a holographic
recording medium 4 on which a hologram 41 is recorded, and a light
detector 5. Further, FIG. 1(B) is a pattern diagram for explaining the
basic principle for a recording device 6 and a method for recording the
hologram 41 on the holographic recording medium 4 in the phase object
identification device 1. It is to be noted that various types of lenses
in the specification include both single lenses and lens groups of
multiple lenses combined.

[0031]The light source 2 emits coherent light in phase, and it is
preferable to use a laser light source as the light source 2. Light 21
emitted from the light source 2 is processed by an optical system, not
shown, into a plane wave which has a larger cross section than the sample
31.

[0032]The sample holding means 3 is provided to place the sample 31 in the
phase object identification device 1, and as the sample holding means 3,
various types of holding means can be selected depending on the sample
31. For example, the sample 31 may be simply placed on the sample holding
means 3, or may be fixed to the sample holding means 3 with vacuum
adsorption, a fixation device, or the like. In order to reduce the
attachment of dirt and dust, the fixed sample 31 is preferably arranged
in a vertical direction, or placed on the undersurface of the sample
holding means 3. In addition, the sample 31 may be secured with a clip or
the like, or in the case of the sample 31 in the form of a thin piece, a
structure can be adopted in which the sample 31 is inserted into a slit
provided in the holding means. While the sample 31 may be directly held
in the sample holding means 3, the sample 31 in an aid such as a
container or a mounting device may be held in the sample holding means 3.
For example, a microplate or prepration with the sample 31 therein may be
held in the sample holding means 3.

[0033]The phase object 31 to be identified may be any phase object which
at least changes the phase of light, which may or may not change the
intensity of light. For example, biological cells, bacteria, gratings,
waveguides, microscopic steps at the surfaces of objects, structure of
the same color, etc. can be used as the phase object 31 to be identified.
In addition, the phase object 31 to be identified is not to be considered
limited to solids, and encompasses, for example, orientation structures
of liquid crystals, and the like.

[0034]The sample holding means 3 and the sample 31 held therein serve as a
sample light production means for modulating at least the phase of the
light 21 emitted from the light source 2 to produce sample light 22.
While the sample 31 is a phase object for modulating at least the phase
of light, the phase object may further modulate the intensity of light.
As shown in FIG. 1(A), in the case of a transmission-type sample light
production means which transmits the light 21 from the light source
through the sample 31 and the sample holding means 3 to produce the
sample light 22, at least a region of the sample holding means 3 in which
the sample 31 is located needs to be configured so as not to block light.
For example, a transparent material may be used for the region of the
sample holding means 3 in which the sample 31 is located, or the sample
31 placed in a transparent container or mounting device may be held by
the sample holding means 3 with an opening in the region of the sample
holding means 3 in which the sample 31 is located. The sample holding
means 3 in such a transmission-type sample light production means can be
used as a mask for producing object light 24 and reference light 25 in
the recording device 6 described later. It is to be noted that in the
case of preparing a reflection-type sample light production means, the
surface of the sample holding means 3 is made with a mirror surface in
such a way that light transmitting through the sample 31 is reflected to
produce sample light 22. The case of a reflection-type sample light
production means requires an optical system such as a beam splitter for
separating the light 21 from the light source for irradiating the sample
holding means 3 and the sample light 22.

[0035]On the holographic recording medium 4, the hologram 41 is recorded
which is formed by interference between reference light 25 and objet
light 24 that is phase-modulated by a known phase object (see FIG. 1(B)
for the object light 24 and the reference light 25). The holographic
recording medium 4 may be a transmission-type or reflection-type
holographic recording medium, and FIG. 1(A) shows a transmission-type
holographic recording medium. The holographic recording medium 4 in FIG.
1(A) has a structure of a hologram recording layer 43 interposed between
a pair of light-transmitting substrates 42 and 44. In the case of
preparing a reflection-type holographic recording medium, a reflective
layer may be provided on the rear side from the hologram recording layer
43 while the light incidence side of the holographic recording medium is
used as a front surface. For example, when a reflective layer is provided
on the front surface or rear surface of the substrate 44, a
reflection-type holographic recording medium can be prepared.

[0036]The known phase object refers to a phase object which has at least
some information or characteristics identified. For example, known phase
objects include phase objects and phase patterns with their phase
modulation patterns identified, biological cells and bacteria with their
names identified, biological cells and bacteria with their active
reactions identified, phase patterns of cell nuclei, specimens of phase
objects (products with microscopic steps and structures of the same
color) within standards (within dimension tolerances), and gratings with
their intervals identified.

[0037]When the hologram 41 of the holographic recording medium 4 is
irradiated with the sample light 22, reproduced light 23 is reproduced
depending on the degree of interference between the sample light 22 and
hologram 41. The reproduced light 23 refers to light corresponding to the
reference light 25 emitted when the hologram 41 is recorded. The
cross-sectional shape and travelling direction of the reference light 25
is reflected on the cross-sectional shape and travelling direction of the
reproduced light 23. The degree of interference corresponds to a
correlation value (the degree of similarity) between the known phase
object with the object light for recording the hologram 41 and the sample
31 which is a phase object to be identified. Therefore, when the sample
31 is the same as the known phase object, the correlation value is the
maximum because of autocorrelation, and intense reproduced light is
reproduced. When the sample 31 is different from but similar to the known
phase object, reproduced light is reproduced which has an intensity
depending on the degree of similarity. Furthermore, when the sample 31 is
completely different from the known phase object, reproduced light is not
reproduced. It is to be noted that the sample light 22 transmitting
through the holographic recording medium 4 (indicated by a dotted line in
FIG. 1(A)) is blocked or separated from the reproduced light 23 by a mask
not shown or an optical system for separation so as not to reach the
light detector 5.

[0038]The light detector 5 is provided to detect the reproduced light 23
reproduced from the hologram 41 of the holographic recording medium 4,
which can preferably detects the light intensity. As the light detector
5, highly sensitive light detection elements such as photomultiplier
tubes (PMT) and avalanche photo diodes, and inexpensive small-sized
semiconductor detectors, for example, PIN photodiodes, CMOS sensors, and
CCD sensors, etc. can be used. When the cross-sectional shape of the
reproduced light 23 is smaller than the light receiving region of the
light detector 5, the light detector including one light detection
element can directly be used. On the other hand, when the cross-sectional
shape of the reproduced light 23 is larger than the light receiving
region of the light detector 5, the light detector including one light
detection element can be used by light collection through a collecting
lens. In addition, the light detector 5 including multiple light
detection elements can be used, and in such a case, the light intensity
of the reproduced light can also be detected by obtaining the sum of the
intensities from all of the light detection elements. Even when the
cross-sectional shape of the reproduced light 23 is smaller than the
light receiving region of the light detector 5, the use of a collecting
lens can improve the reliability. It is to be noted that the
cross-sectional shape of the reproduced light 23 is determined by the
cross-sectional shape of the reference light for recording.

[0039]As described above, the detection of the presence or absence of the
reproduced light 23 can identify whether or not the phase object 31 to be
identified is correlated with the known phase object. More specifically,
unless any reproduced light is reproduced from the hologram irradiated
with the sample light under the same condition as in the case of
recording, the phase object to be identified can be identified as having
no correlation with the known phase object. If reproduced light is
generated, the phase object to be identified can be identified as having
a correlation with the known phase object. Furthermore, the detection of
the intensity of the reproduced light also allows the degree of
correlation to be identified.

[0040]For example, even in the case of only identifying the presence or
absence of any correlation, the use of a known biological cell or
bacterium with a cell nucleus as the known phase object and the use of a
collected and cultured biological cell or bacterium as the phase object
to be identified makes it possible to utilize the identification of the
presence or absence of correlation for an examination for identifying
whether or not the collected and cultured biological cell or bacterium
has a cell nucleus. In addition, the identification with the use of a
specimen within standards as the known phase object and with the use of a
produced product as the phase object to be identified makes it possible
to identify whether or not the produced product corresponds to the
standards. For example, the identification can be utilized for
examinations on errors in diffraction grating period of grating elements
and on the three-dimensional shapes of structures of the same color. In
these examinations, the sample holding means 3 is preferably provided
with a sample conveying means for sequentially conveying the samples 31
to the sample holding means 3 in order to examine a large number of
samples continuously.

[0041]In addition, multiple holograms 41 are irradiated with the sample
light 22 to identify the presence or absence of correlation with multiple
known phase objects, thereby allowing the sample 31 to be specified. In
order to irradiate the multiple holograms 41 with the sample light 22, it
is more preferable to record, on the holographic recording medium 4,
multiple holograms 41 formed with the use of multiple known phase objects
and provide a irradiated position shifting means for shifting the
position irradiated with the sample light 22 in the holographic recording
medium 4, while the holographic recording medium 4 itself may be replaced
with another holographic recording medium 4 on which a hologram 41 is
recorded and irradiated with the sample light 22.

[0042]While the irradiated position shifting means includes a system of
shifting the sample light 22, a system of shifting the holographic
recording medium 4, and a system of shifting both the sample light 22 and
the holographic recording medium 4, the system of fixing the sample light
22 and shifting the holographic recording medium 4 is preferable in order
to prevent the position of the optical system from getting out of
alignment due to vibrations, etc. associated with shifting. For example,
the holographic recording medium 4 may be shifted with the use of a XY
stage in planar directions orthogonal to the optical axis, or the
holographic recording medium 4 may be rotated with the use of a motor.

[0043]The recording device 6 in FIG. 1(B) is intended to produce the
holographic recording medium 4 for use in the phase object identification
device 1, which irradiates the holographic recording medium 4 with the
object light 24 and the reference light 25 and records, on the
holographic recording medium 4, the hologram 41 formed by interference
between the object light 24 and the reference light 25. The hologram 41
herein recorded on the holographic recording medium 4 in the recording
device 6 has to interfere with the sample light 22 to generate the
reproduced light 23 in the phase object identification device 1. For this
purpose, it is necessary to irradiate the holographic recording medium 4
with the object light 24 which has the same wavelength as the sample
light 22 under the same irradiation conditions (incidence angle,
magnification ratio, focal point). As the simplest approach, the
configuration of the phase object identification device 1 for generating
the sample light 22 and irradiating the holographic recording medium 4
with the sample light 22 may be conformed to the configuration of the
recording device 6 for generating the object light 24 and irradiating the
holographic recording medium 4 with the object light 24. This approach
means that a device can be produced which has the both functions of the
phase object identification device 1 and the recording device 6. However,
the light detector 5 for detecting reproduced light is separately
required for the phase object identification device 1, whereas a
reference light generation means for generating reference light is
separately required for the recording device 6. In this specification,
the descriptions of the respective configurations of the phase object
identification device 1 or the recording device 6 are basically
incorporated in the description of the common configuration of the other
device.

[0044]The recording device 6 in FIG. 1(B) uses the same configuration
(denoted by the same reference numerals) as the configuration in FIG.
1(A) for generating the sample light 22 and irradiating the holographic
recording medium 4 with the sample light 22 in the same arrangement. More
specifically, the recording device 6 in FIG. 1(B) includes the light
source 2, the sample holding means 3, and the holographic recording
medium 4. However, in the recording device 6, the sample holding means 3
holds a known phase object 32, and the sample holding means 3 and the
known phase object 32 serve as an object light generation means for
generating the object light 24 with the use of light 21 from the light
source 2. In addition, the holographic recording medium 4 is irradiated
with the reference light 25 generated by a reference light generation
means, not shown. The hologram formed by interference between the object
light 24 and the reference light 25 can cause a photoreaction of a
photosensitive material in the hologram recording layer 43 and set the
hologram 41 in the hologram recording layer 43.

[0045]In the case of recording multiple holograms 41 on the holographic
recording medium 4, the irradiated position shifting means may be used to
shift the positions irradiated with the object light 24 and the reference
light 25 in the holographic recording medium and irradiate other
positions with object light 24 formed by another known phase object 32
and reference light 25 to record another hologram 41.

[0046]As the object light generation means, a phase spatial light
modulator can also be used, besides the method of using the known phase
object 32. As the phase spatial light modulator, for example, a
phase-modulation type liquid crystal display device can be adopted, on
which a phase pattern of a known phase object may be displayed. In the
case of using the phase spatial light modulator, simply changing the
display on the phase spatial light modulator can preferably generate
another object light when multiple holograms 41 are to be recorded.

[0047]While the reference light generation means preferably generates the
reference light 25 with the use of light 11 from the light source 1,
light from other light source may be used which interferes with the
object light 24. The holographic recording medium 4 is irradiated with
the reference light 25 so as to intersect with the object light 24. For
the reference light, divergent light in a smaller region as compared with
the object light and a bundle of spatially separated multiple rays can be
used. While a two-beam interference type optical system can also be used
in which the optical axis of the object light 24 is different from the
axis of the reference light 25, it is preferable to record the hologram
41 with the use of a collinear optical system. The collinear optical
system will be described in detail with reference to FIG. 2.

[0048]While the present invention has been described with reference to the
minimum required configurations in FIGS. 1(A) and 1(B) in order to
explain the basic principle, the present invention is not to be
considered limited to devices which have only the configurations, and
even more configurations can be added in response to desired effects. For
example, it is preferable to record a Fourier image of the known phase
object 32 as the hologram 41, rather than recording a real image of the
known phase object 32. For this purpose, an objective lens arranged so
that real images of the sample light 22 and the object light 24 are
located on the incident pupil plane may be adopted in such a way that the
objective lens is used to irradiate the holographic recording mediums
with the sample light 22 and the object light 24. The Fourier image is
not the shape of a phase pattern, but the spatial frequency distribution
of a phase pattern, and thus allows tendency correlation of a pattern to
be identified, rather than simple shape correlation.

[0049]In addition, it is also preferable to include an observation optical
system for observing the sample 31 and the known phase object 32.
Furthermore, in order to identify multiple samples continuously, the
sample holding means 3 preferably includes a sample conveying means for
sequentially conveying the multiple samples 31.

[0050]FIG. 2 is a configuration diagram schematically illustrating an
embodiment of a phase object identification device 1 which is also
available as a recording device 6 for recording a hologram 41 with the
use of a collinear optical system. The phase object identification device
1 in FIG. 2 further includes an observation optical system 7 and an image
sensor 71 for observation for observing a sample or a known phase object
(hereinafter, the sample and the known phase object are collectively
referred to as "a sample and the like"). It is to be noted that a
reflection-type holographic recording medium 4 is used in the phase
object identification device 1 in FIG. 2.

[0051]The phase object identification device 1 includes an optical system
for generating sample light, irradiating the holographic recording medium
4 with the sample light, and detecting reproduced light, in addition to a
light source 2, a sample holding means 3, a holographic recording medium
4, and a light detector 5, and the optical system also includes the
observation optical system 7 for observing a sample and the like. The
optical system includes a beam shaping optical system 51, a pair of
mirrors 52, a sample-side objective lens 53, an imaging lens 54, a beam
splitter 55, a mask 56, a polarization beam splitter 57, a first relay
lens 58, a second relay lens 59, a quarter wavelength plate 60, an
objective lens 61, an aperture 62, and a collecting lens 63.

[0052]The light source 2 serves as a light source for object light and
reference light for recording a hologram, and also serves as a light
source for sample light for identifying a sample 31. Furthermore, in FIG.
2, the sample light 2 is also used as a light source for observing a
sample and the like in the observation optical system 7. However, it is
preferable to separately prepare a light source which is suitable for
observation, rather than the light source 2, as the light source for the
observation optical system. As the light source 2, for example, a YVO4
laser of 532 nm can be used. It is to be noted that as the light source
2, light is selected which has a wavelength to which a photosensitive
material in a hologram recording layer 43 of the holographic recording
medium 4 is sensitive.

[0053]The beam shaping optical system 51 is provided, if necessary, for
converting the shape of light emitted from the light source 2, and for
example, includes a collimator lens for processing divergent light into
parallel light, and a beam expander for increasing the apertures of
beams.

[0054]The pair of mirrors 52 is provided to direct the travelling
direction of light emitted from the light source 2 to a sample and the
like. In FIG. 2, the pair of mirrors 52 changes the travelling direction
of light emitted from the light source 2 by 180° to reduce the
size of the device. The means for directing the travelling direction of
light to a sample and the like is not to be considered limited to the
configuration of the pair of mirrors 52, and an appropriate configuration
is adopted as the means, depending on the configuration of the optical
system. For example, prisms, deflection elements, and the like can also
be used instead of mirrors, or if the travelling direction of light
emitted from the light source 2 is directly directed to a sample and the
like, the means for directing the travelling direction of light to a
sample and the like is never necessary.

[0055]The sample holding means 3 is provided to hold a sample and the
like. In FIG. 2, the sample holding means 3 has an opening for a region
to be irradiated with light, and the sample 31 is held in the opening
region. In the phase object identification device 1 in FIG. 2, the sample
and the like held in the sample holding means 3 can be observed by the
observation optical system 7 and the image sensor 71 for observation.

[0056]The observation optical system 7 is intended to form an image of a
sample and the like on a light receiving surface of the image sensor 71
for observation and a plane 33 (the position in which the mask 56 is
placed) conjugate to the light receiving surface, and an incident pupil
plane 35 of an objective lens, and it is possible for the observation
optical system 7 to use optical systems of various types of microscopes.
In FIG. 2, the observation optical system 7 includes the sample-side
objective lens 53 and the imaging lens 54, which allows a sample and the
like to be observed in a bright field. In the case of a small sample and
the like, the sample-side objective lens 53 and the imaging lens 54 can
preferably enlarge an image of a sample and the like. In addition, for
the sample-side objective lens 53, multiple lenses which are different in
magnification ratio can be preferably switched in order to make the
observation easier. Furthermore, an eyepiece for observation by the naked
eye may be provided in combination with the imaging lens 54 or instead of
the imaging lens 54.

[0057]Furthermore, in the case of including the observation optical system
7 as shown in FIG. 2, the sample holding means 3 preferably includes a
focusing means 36 for adjusting the focal points of a sample and the like
and/or a sample positioning means 37 for adjusting the positions of a
sample and the like. The focusing means 36 is a means for shifting the
phase object (sample 31) to be identified and the known phase object 32
in the direction of the optical axis, which is provided to form an image
of a sample and the like on imaging planes (the light receiving surface
of the image sensor 71, the position 33, and the position 35). The
focusing means 36 is used to shift the sample 31 and the like manually or
electrically in the direction of the optical axis (Z axis direction). In
addition, the sample positioning means 37 is a means for shifting the
phase object (sample 31) to be identified and the known phase object 32
in the planar directions orthogonal to the optical axis, which is
provided to place the sample 31 and the like in the field for
observation. The sample positioning means 37 is used to shift the sample
31 and the like manually or electrically in the planar directions (X axis
direction and Y axis direction) orthogonal to the optical axis. Various
types of moving mechanism can be used as the focusing means 36 and the
sample positioning means 37, and for example, a XYZ driven stage or the
like can be used which includes an adjusting mechanism for slight
movements.

[0058]As the image sensor 71 for observation, CCDs and CMOS sensors can be
used. The image sensor 71 for observation is connected to a monitor or a
recording medium, not shown, so that images acquired by the image sensor
71 for observation, can be displayed on the monitor or recorded on the
recording medium. When the focusing means 36 and the sample positioning
means 37 are used to make an adjustment so that an image of a sample and
the like is formed on the center of the optical axis while observing the
sample and the like by the image sensor 71 for observation, the accuracy
of identification can be improved dramatically. In addition, when the
observation optical system 7 is used to adjust the magnification ratio
for the sample and the like, the size of the phase object to serve as a
basis for the object light and the sample light can be standardized. The
observation optical system 7 forms, in the position 33, the same image as
the image formed on the light receiving surface of the image sensor 71
for observation, and the holographic recording medium 4 is irradiated
with the image in the position 33 as sample light and object light. When
the image in the position 33 (the image observed by the image sensor 71
for observation) is formed to have the same size, the difference in size
between a sample and the like can be corrected.

[0059]It is possible to utilize the configurations of conventional optical
microscopes for the observation optical system 7, the sample holding
means 3, the focusing means 36, the sample positioning means 37, and the
image sensor 71 for observation, which are provided to observe the sample
31 and the like. Since the observation in a bright field is difficult
when the intensity of light is not modulated by the sample and the like
or when the difference in intensity is small, it is preferable to adopt
observation in a dark field or a configuration in which the observation
is possible even with the use of a phase-contrast microscope or a
differential interference microscope.

[0060]The beam splitter 55 is an optical element which partially reflects
incident light and transmits the other of the incident light, and splits
light from a sample and the like to generate light directed to the image
sensor 71 for observation and light directed to the holographic recording
medium 4. The beam splitter 55, which divides light, may be provided with
an optical element for switching the travelling direction of light. For
example, a movable mirror can be provided instead of the beam splitter
55, in such a way that light from a sample and the like can be reflected
toward the image sensor 71 for observation in the case of observing a
sample and the like, and the mirror can also be moved out of the optical
axis to direct light from the sample and the like toward the holographic
recording medium 4 in the case of identifying the sample and the like.

[0061]The mask 56 is arranged on the imaging plane on which an image of
the sample and the like is formed by the observation optical system 7 or
in the position of the sample holding means. For identification, a mask
is arranged for forming the profile of sample light, and for recording,
another mask is arranged for forming the profile of object light and
producing the intensity pattern of reference light. The mask 56 may be
arranged in the position of the sample and the like (that is, the sample
holding means 3) or on other imaging plane (the incident pupil plane 35
of the objective lens), rather than in the position 33. For example, the
profile of the sample light, the profile of the object light, and the
intensity pattern of reference light may be formed with the opening of
the sample holding means 3 as the mask 56, or the mask 56 may be arranged
on the incident pupil plane 35 of the objective lens. It is to be noted
that the generation of the sample light and object light themselves is
achieved by being modulated by the sample and the like, whereas the mask
56 is provided to form the profiles of the sample light and object light.

[0062]FIG. 3(A) is an example of a mask 56 for forming the profile of
sample light in the case of identification, and FIG. 3(B) is an example
of a mask 56 for producing the profile of object light and the intensity
pattern of reference light in the case of recording. In FIG. 3(A), the
mask 56 has a circular opening 56a provided in the center, and light can
be transmitted through the mask 56 to form the profile of the sample
light into a circular shape. In FIG. 3(B), the mask 56 has a circular
opening 56b provided in the center, and twelve small circular openings
56c provided in a radial fashion around the circular opening 56b, and
light can be transmitted through the opening 56b and the openings 56c
respectively to form the profile of the object light into a circular
shape and generate reference light arranged in a pattern composed of
twelve small circular shapes arranged in a radial fashion around the
object light. The mask 56 is formed from a material which is able to
block light from the light source 2. It is to be noted that the mask for
recording and the mask for identification may be switched by flip of a
switch, or the openings 56c may be provided with a shutter to close the
shutter for identification.

[0063]The polarization beam splitter 57 is provided to transmit one of
mutually orthogonal polarization directions and reflects the other, and
provided along with the quarter wavelength plate 60 in order to separate
sample light, object light, and reference light toward the holographic
recording medium 4 from reproduced light reproduced from the holographic
recording medium 4. In FIG. 2, the polarization beam splitter 57
transmits the sample light, object light, and reference light toward the
holographic recording medium 4, and reflects the reproduced light
reproduced from the holographic recording medium 4 toward the light
detector 5. Depending on the configuration of the optical system, the
polarization beam splitter 57 may be configured so as to reflect the
sample light, object light, and reference light toward the holographic
recording medium 4 and transmit the reproduced light toward the light
detector 5.

[0064]The first relay lens 58 and the second relay lens 59 are an example
of an optical system for forming an image of a sample and the like formed
in the position 33 onto the incident pupil plane 35 of the objective lens
61. The first relay lens 58 is arranged so that the interval from the
position 33 to the first relay lens 58 and the interval from the first
relay lens 58 to a Fourier plane 34 correspond to the focal length of the
first relay lens 58. In addition, the second relay lens 59 is arranged so
that the interval from the Fourier plane 34 to the second relay lens 59
and the interval from the second relay lens 59 to the incident pupil
plane 35 correspond to the focal length of the second relay lens 59. The
optical system is not to be considered limited to the configuration of
the first and second relay lenses 58 and 59, and various imaging optical
systems can be used.

[0065]The quarter wavelength plate 60 is provided to convert linearly
polarized light into circularly polarized light. Light can be transmitted
through the quarter wavelength plate 60 twice to rotate linearly
polarized light by 90 degrees. Reproduced light reproduced from the
hologram 41 by sample light irradiation corresponds to reference light
for recording. The reference light has been once transmitted through the
quarter wavelength plate 60 when the hologram 41 is to be recorded, thus,
the transmission of the reference light through the quarter wavelength
plate 60 again results in linearly polarized light in a polarization
direction which is orthogonal as compared with the reference light before
the transmission through the quarter wavelength plate 60 for recording,
and the linearly polarized light can be separated by the polarization
beam splitter 57.

[0066]The objective lens 61 is provided to apply Fourier transformation to
sample light, object light, and reference light and irradiate the
holographic recording medium 4 with the sample light, object light, and
reference light. In addition, when the reflection-type holographic
recording medium 4 is used as shown in FIG. 2, the objective lens 61
forms an image of reproduced light reproduced from the hologram 41 onto
an exit pupil plane. In order to apply Fourier transformation to sample
light, object light, and reference light, the imaging optical systems 53,
54, 58, and 59 are used to form an image of a sample and the like or the
intensity pattern of reference light onto the incident pupil plane 35 of
the objective lens 61.

[0067]The holographic recording medium 4 in FIG. 2 has a reflection-type
structure of a hologram recording layer 43 interposed between a
transparent substrate 42 and a substrate 44 with a reflective layer. When
the phase object identification device 1 functions as the recording
device 6, the holographic recording medium 4 is irradiated with object
light and reference light to record the hologram 41 on the hologram
recording layer 43. Alternatively, when the phase object identification
device 1 identifies a phase object, the holographic recording medium 4 is
irradiated with sample light, and the sample light is emitted from the
incidence plane side of the holographic recording medium 4, along with
reproduced light reproduced from the hologram 41.

[0068]The holographic recording medium 4 is held on a recording medium
shifting means 45 for shifting the holographic recording medium 4. The
recording medium shifting means 45 is able to shift or rotate the
holographic recording medium 4 in directions orthogonal to the optical
axis, in such a way that the positions irradiated with sample light,
object light, and reference light in the holographic recording medium 4
can be shifted to record multiple holograms on the holographic recording
medium 4 and optical correlation can be calculated between the multiple
holograms 41 on the holographic recording medium 4 and sample light.

[0069]The aperture 62 has an opening which blocks sample light reflected
by the reflection-type holographic recording medium 4 and transmits only
reproduced light reproduced from the holographic recording medium 4 to
the light detector 5. The aperture 62 is placed between the polarization
beam splitter 57 and the collecting lens 63, and preferably placed in the
imaging plane of sample light, for example, the focal plane of the first
relay lens 58 (the position conjugate to the position 33) in order to
reduce noises caused by diffracted light of the sample light. FIG. 3(C)
is an example of the aperture 62, in which twelve small circular openings
62a arranged in a radial fashion are provided which correspond to the
openings 56c in the mask 56 for recording shown in FIG. 3(B).

[0070]The collecting lens 63 is provided to collect reproduced light into
the light receiving region of the light detector 5, and believed to be
available even for a light detector 5 including one light detection
element.

[0071]The light detector 5 is intended to detect the light intensity of
reproduced light reproduced from the holographic recording medium 4.
Since the reproduced light is collected by the collecting lens 63 into a
small region, a light detector 5 including one light detection element
can also be used.

[0072]Next, the operation for each processing in the phase object
identification device 1 in FIG. 2 will be briefly described. First, in
the case of observing a sample and the like, light emitted from the light
source 2 is shaped by the beam shaping optical system 51 to provide a
required aperture and parallel light, reflected by the pair of mirrors 52
to irradiate the sample and the like, passed through the sample-side
objective lens 53 and the imaging lens 54, and reflected by the beam
splitter 55 to reach the image sensor 71 for observation. An image of the
sample and the like is formed on the light-receiving surface of the image
sensor 71 for observation by the sample-side objective lens 53 and the
imaging lens 54. Then, the sample positioning means 37 is used to adjust
the position of the image and the like so that an image of the sample and
the like is arranged in the center in the light-receiving surface of the
image sensor 71 for observation, whereas the focusing means 36 is used to
make an adjustment so that an image of the sample and the like is brought
into focus on the light-receiving surface. With the sample and the like
observed as described, the image of the sample and the like is also
arranged in the center in the imaging plane 33, and brought into focus,
and the reliability in identification and the uniformity in recording can
be kept by continuously carrying out the processing for identification
and the processing for recording.

[0073]In the case of identifying the sample 31 by the phase object
identification device 1 in FIG. 2, light emitted from the light source 2
is shaped by the beam shaping optical system 51 to provide a required
aperture and parallel light, and reflected by the pair of mirrors 52 to
irradiate the sample 31. At least the phase of the light is spatially
modulated by the sample 31, and an image of the sample 31 is formed in
the position 33 by the sample-side objective lens 53 and the imaging lens
54. The mask 56 in FIG. 3(A) is placed in the position 33, which produces
sample light with a circular profile. Then, the sample light is
transmitted through the polarization beam splitter 57, formed into an
image on the incident pupil plane of the objective lens 61 by the first
and second relay lenses 58 and 59, converted by the quarter wavelength
plate 60 into circularly polarized light, and subjected to Fourier
transformation by the objective lens 61 to irradiate the hologram 41
recorded on the hologram recording layer 43 of the holographic recording
medium 4. As a result, the interference between the hologram 41 and the
sample light reproduces reproduced light corresponding to reference light
for recording if there is a correlation between the hologram 41 and the
sample light.

[0074]The sample light and reproduced light reflected by the reflective
layer is emitted from the holographic recording medium 4, and passed
through the objective lens 61, the quarter wavelength plate 60, the
second relay lens 59, and the first relay lens 58 in the direction
opposite to the direction for irradiation to enter the polarization beam
splitter 57. The reproduced light corresponds to reference light for
recording, and the reference light is passed through the quarter
wavelength plate 60 for conversion into circularly polarized light when
the holographic recording medium 4 is irradiated with the reference
light. Thus, the light as reproduced light is again passed through the
quarter wavelength plate 60 to convert the reproduced light into linearly
polarized light in a polarization direction orthogonal to the reference
light. Therefore, the reproduced light is reflected by the polarization
beam splitter 57 which transmits the reference light, passed through the
aperture 62, and collected by the collecting lens 63 into the light
detector 5. It is to be noted that the sample light reflected by the
reflective layer is emitted from the holographic recording medium 4,
passed through the optical systems in the same way as the reproduced
light, and reflected by the polarization beam splitter 57, but blocked by
the aperture 62.

[0075]Furthermore, in order to use multiple holograms 41 for
identification, the holographic recording medium 4 is shifted or rotated
by the recording medium shifting means 45 while irradiating with sample
light in a continuous or pulsed way. Then, the multiple hologram 41
recorded on the holographic recording medium 4 can be irradiated with the
sample light in a continuous or intermittent way, and reproduced light
can be also detected in a continuous or intermittent way.

[0076]The light intensity of the reproduced light varies according to the
correlation value (the degree of similarity) between the object light for
recording the hologram 41 and the sample light. The larger the value of
the light intensity is, the more the object light is similar to the
sample light. Therefore, when the light intensity of the reproduced light
exceeds a threshold value determined in advance by experiment or the
like, the sample 31 can be identified as a phase object which is
coincident with or similar to the known phase object for recording of the
hologram 41 reproducing the reproduced light. Alternatively, when
reproduced light exceeding the threshold value is not detected, the
sample 31 can be identified as a phase object which is not coincident
with or similar to the known phase object recorded as the hologram 41 on
the holographic recording medium 4. Further, when the intensities of
reproduced light from multiple holograms exceed the threshold value, the
reproduced light of the highest light intensity is preferably output
first as an identification result of similarity.

[0077]In the case of recording a known phase object by the phase object
identification device 1 in FIG. 2, the sample holding means 3 holds the
known phase object. Light emitted from the light source 2 is shaped by
the beam shaping optical system 51 to provide a required aperture and
parallel light, and reflected by the pair of mirrors 52 to irradiate the
known phase object. At least the phase of the light is spatially
modulated by the known phase object, and an image of the known phase
object is formed in the position 33 by the sample-side objective lens 53
and the imaging lens 54. The mask 56 in FIG. 3(B) is placed in the
position 33, which produces object light with a circular profile and
twelve small circular rays of reference light arranged around the object
light. Then, the object light and reference light is transmitted through
the polarization beam splitter 57, formed into an image on the incident
pupil plane of the objective lens 61 by the first and second relay lenses
58 and 59, converted by the quarter wavelength plate 60 into circularly
polarized light, and subjected to Fourier transformation by the objective
lens 61 to irradiate the hologram recording layer 43 of the holographic
recording medium 4. As a result, a hologram 41 formed by interference
between the object light and the reference light is recorded on the
hologram recording layer 43 of the holographic recording medium 4.

[0078]FIG. 4 is modification examples of the sample holding means 3, in
which the function of the mask 56 is added to the sample holding means
56. FIG. 4(A) is a cross-sectional view of the sample holding means 3 for
recording, FIG. 4(B) is a plan view of FIG. 4(A), and FIG. 4(C) is a
cross-sectional view of the sample holding means 3 for identification. In
FIG. 4(A), the sample holding means 3 includes a pair of light-blocking
plate-like members 3a and 3b, slide glass 38a and cover glass 38b with a
known phase substance 32 interposed therebetween are arranged between the
pair of plate-like members 3a and 3b, and clips 3c clip the pair of
plate-like members 3a and 3b to hold the known phase substance 32 via the
slide glass 38a and the cover glass 38b. The pair of plate-like members
3a and 3b is provided with openings 56b and 56c as shown in FIG. 4(B). It
is to be noted that FIG. 4(A) is a cross section of FIG. 4(B) along the
like A-A, and the opening sections are indicated by dotted lines in FIG.
4(A). In the region of the circular opening 56b in the center, the known
phase substance 32 is placed which modulates the phase of light from the
light source to generate object light. In addition, the openings 56c
arranged in a radial fashion around the circular opening 56b generate
reference light arranged in a pattern composed of twelve small circular
shapes arranged in a radial fashion around the object light. In the
configuration of FIG. 4(A), the transparent aids (including colored
transparent aids) such as the slide glass 38a and the cover glass 38b
enclosing the known phase substance 32 are present in both the opening
56b for generating object light and the openings 56c for generating
reference light. Thus, the changes in phase and intensity caused by the
aids can be cancelled to record only changes in phase due to the known
phase substance 32.

[0079]For identification, as shown in FIG. 4(C), a phase object 31 to be
identified is enclosed instead of the known phase object 32 between slide
glass 38a and cover glass 38b, on which a pair of plate-like members 3a
and 3b, and further, a light-blocking member 3d provided with an opening
56a only in the center like the mask 56 in FIG. 3(A) are put, and clipped
by clips 3c. The phase object 31 to be identified, which is placed in the
region of the opening 56a, can generate sample light with the use of
light from the light source, without generating reference light. It is to
be noted that the intensity pattern of the reference light is not to be
considered limited to the shape and number as in the case of the openings
56c in FIG. 3(B) and FIG. 4(B), as long as at least one opening generates
reference light.

[0080]When the sample holding means 3 is provided with a sample conveying
means for sequentially conveying samples 31, the identification of a
large number of samples can be carried out continuously. FIG. 5 is an
example of the sample conveying means. FIGS. 5(A) and 5(B) are
respectively a cross-sectional view and a plan view of belt-conveyer-type
sample conveying means 39a and 39b, whereas FIGS. 5(C) and 5(D) are
respectively a cross-sectional view and a plan view of
conveying-robot-arm-type sample conveying means 40a and 40b. In FIGS.
5(A) and 5(B), the upper and lower edges of samples 31 are held by
parallel belt conveyers 39a and 39b, and the samples 31 are sequentially
conveyed down the sample-side objective lens 53 by shifting the belt
conveyers 39a and 39b. In FIGS. 5(A) and 5(B), the belt conveyers 39a and
39b serve as both the sample holding means 3 and sample conveying means.
It is to be noted that, although not shown in the figures, a conveying
means for loading the samples 31 onto the belt conveyers 39a and 39b and
a conveying means for unloading the samples 31 on the belt conveyers 39a
and 39b are respectively provided on the right side and left side of the
belt conveyers 39a and 39b in FIG. 5.

[0081]In FIGS. 5(C) and 5(D), conveying robot arms 40a and 40b each have a
turnable pillar provided with a three-step arm unit in a movable manner
in the up-and-down direction and in an extensible manner. The tip of the
third arm section from the bottom is configured to be wide so that the
samples 31 are placed on the tip. The sample holding means 3 is provided
with a concave section 3e in the horizontal direction in the figure, and
the tips of the wide arm sections of the conveying robot arms 40a and
40b, on which the samples 31 are placed, should be able to be inserted
under the samples 31. The conveying robot arm 40a is intended to convey
the samples 31 to the sample holding means 3, whereas the conveying robot
arm 40b is intended to carry the samples 31 out of the sample holding
means 3. It is to be noted that in FIG. 5(D), a window 56a of a
light-transmitting member for transmitting light is provided under the
sample 31 on the sample holding means 3 in such a way that the sample 31
is irradiated with light from the light source to enter the sample-side
objective lens 53.

[0082]FIG. 6 is an embodiment of a recording device 80 for recording a
hologram 41 on a holographic recording medium 4, in which a phase spatial
light modulator is adopted as a part of an object light generation means,
and the recording device 80 also functions as a phase object
identification device with the addition of a configuration for detecting
reproduced light. The recording device 80 includes a light source 81, a
collimator lens 82, a beam splitter 83, a phase spatial light modulator
84, an information processing device 85, a first relay lens 86, a mirror
87, a second relay lens 88, a mask 89, a polarization beam splitter 90, a
quarter wavelength plate 91, an objective lens 92, an aperture 93, a
mirror 94, a collecting lens 95, and a light detector 96. FIG. 6 is also
a case of a reflection-type holographic recording medium 4.

[0083]Light emitted from the light source 81 is shaped into substantially
parallel light by the collimator lens 82, and reflected by the beam
splitter 83 to enter the phase spatial light modulator 84. The phase
spatial light modulator 84 including a plurality of pixels is able to
change the phase of incident light for each pixel and spatially modulate
the phase of light. FIG. 6 shows a reflection type in which a phase
pattern input from the information processing device 85 is displayed on
the phase spatial light modulator 84 which reflects incident light while
modulating the phase of the incident light in accordance with the
displayed phase pattern. As the phase spatial light modulator 84, a
parallel-aligned liquid crystal spatial light modulator (PAL-SLM), etc.
can be used.

[0084]The light reflected by the phase spatial light modulator 84 has a
phase modulated in accordance with the phase pattern input from the
information processing device 85 as described above. Then, light
transmitted through the beam splitter 83 is transmitted by the first and
second relay lenses 86 and 88 so that an image of the phase pattern is
formed on the incident pupil plane of the objective lens 92. On the way,
the light is reflected to change the travelling direction by the mirror
87 arranged in the focal position (Fourier plane) between the first and
second relay lenses 86 and 88. The mask 89 is provided to form the
profile of object light 97 and the intensity pattern of reference light
98, and preferably arranged on the incident pupil plane of the objective
lens 92 and the imaging plane formed by the first and second relay lenses
86 and 88. It is to be noted that if the short focal length of the
objective lens 92 makes it physically difficult to arrange the mask 89 on
the incident pupil plane in the configuration of FIG. 6, an imaging
optical system, not shown, may be further incorporated to arrange the
mask 89 in a position conjugate to the incident pupil plane. After that,
the light is transmitted through the polarization beam splitter 90,
converted by the quarter wavelength plate 91 into circularly polarized
light, and subjected to Fourier transformation by the objective lens 92
to irradiate a hologram recording layer 43 of the holographic recording
medium 4. As a result, a hologram 41 formed by interference between the
object light 97 and the reference light 98 is recorded on the hologram
recording layer 43.

[0085]In addition, in the recording device 80 in FIG. 6, the phase pattern
displayed on the phase spatial light modulator 84 is intended to change
the phase of light, which can be said to be a kind of phase object. Then,
when any phase pattern is displayed on the phase spatial light modulator
84 as a phase object to be identified, the mask 89 can be changed to
carry out processing for identification with the use of the hologram 41
recorded on the holographic recording medium 4. In this case, the phase
spatial light modulator 84 serves as a sample holding means.

[0086]In the case of allowing the recording device 80 in FIG. 6 to
function as a phase object identification device, light emitted from the
light source 81 is shaped into substantially parallel light by the
collimator lens 82, and reflected by the beam splitter 83 to enter the
phase spatial light modulator 84 which reflects the light while
modulating the phase of the light in accordance with a phase pattern
displayed on the phase spatial light modulator 84. The light reflected by
the phase spatial light modulator 84 is transmitted through the beam
splitter 83 and transmitted by the first and second relay lenses 86 and
88 so that an image of the phase pattern is formed on the incident pupil
plane of the objective lens. On the way, the light is reflected to change
the travelling direction by the mirror 87 arranged in the focal position
(Fourier plane) between the first and second relay lenses 86 and 88. The
mask 89 is provided to form the profile of the sample light, while light
is blocked by the opening for shaping the reference light 98 for
recording. After that, the sample light is transmitted through the
polarization beam splitter 90, converted by the quarter wavelength plate
91 into circularly polarized light, and subjected to Fourier
transformation by the objective lens 92 to irradiate the hologram 41
recorded on a hologram recording layer 43 of the holographic recording
medium 4. As a result, the interference between the hologram 41 and the
sample light reproduces reproduced light corresponding to the reference
light for recording.

[0087]The sample light and reproduced light reflected by the reflective
layer is emitted from the holographic recording medium 4, and passed
through the objective lens 92 and the quarter wavelength plate 91 in the
direction opposite to the direction for irradiation to enter the
polarization beam splitter 90. The reproduced light corresponds to
reference light for recording, and the reference light is passed through
the quarter wavelength plate 91 for conversion into circularly polarized
light when the holographic recording medium 4 is irradiated with the
reference light. Thus, the light as reproduced light is again passed
through the quarter wavelength plate 91 to convert the reproduced light
into linearly polarized light in a polarization direction orthogonal to
the reference light. Therefore, the reproduced light is reflected by the
polarization beam splitter 90 which transmits the reference light. In
addition, the reflected sample light is also passed through the quarter
wavelength plate 91 twice, and thus reflected by the polarization beam
splitter 90. The reproduced light is passed through an opening of the
aperture 93, whereas the sample light is blocked by the aperture 93. The
reproduced light reflected by the mirror 94 is collected by the
collecting lens 95 into the light detector 96. It is to be noted that
while FIG. 6 shows only one opening for shaping object light and only one
opening for shaping reference light as openings of the mask 89 for the
sake of convenience, reference light may have multiple intensity
patterns.

EXAMPLE 1

[0088]The device 80 in FIG. 6 was used to demonstrate the possibility of
identifying phase objects. In this example, a Nd:YVO4 laser of 532 nm was
used as the light source 81. As the mask 89, masks in the shapes shown in
FIGS. 3(A) and 3(B) were used. More specifically, the mask for
identification was a mask with a circular opening 56a in the center for
generating sample light, whereas the mask for recording was a mask with a
circular opening 56b in the center for generating object light and with
twelve small circular openings 56c around the circular opening 56b in a
radial fashion for generating reference light. The openings 56a and 56b
for the profile of sample light or object light had a circular shape with
a diameter of 1 mm, whereas the openings 56c for generating reference
light had a circular shape with a diameter of 0.29 mm. In addition, the
objective lens 92 had NA of 0.55 and a focal length of 4 mm.

[0089]First, four types of holograms 41 were recorded on the holographic
recording medium 4. Phase patterns in FIGS. 7(A) to 7(D) were displayed
on a display region of 32×32 pixels of the phase spatial light
modulator 84 to generate object light for each phase pattern, and record
holograms by interference between the object light and the reference
light. FIGS. 7(A) to 7(D) show phase patterns on the display surface on
the left side, and show the phase modulation degrees in cross sections
along an alternate long and short dash line or an alternate long and two
short dashes line on the right side. FIG. 7(A) displays a circular
pattern 101 with a phase modulation degree of π/2 and a diameter of 32
pixels in a display region 100. FIG. 7(B) displays a circular pattern 101
with a phase modulation degree of π/2 and a diameter of 32 pixels in a
display region 100 and displays a circular pattern 102 with a phase
modulation degree of π and a diameter of 10 pixels in the center of
the circular pattern 101. FIG. 7(C) displays a circular pattern 101 with
a phase modulation degree of π/2 and a diameter of 32 pixels in a
display region 100 and displays two circular patterns 102 with a phase
modulation degree of π and a diameter of 10 pixels in the center of
the circular pattern 101. FIG. 7(D) displays a circular pattern 101 with
a phase modulation degree of π/2 and a diameter of 32 pixels in a
display region 100 and displays three circular patterns 102 with a phase
modulation degree of π and a diameter of 10 pixels in the center of
the circular pattern 101. It is to be noted that FIG. 7(D) shows the
phase modulation degrees in a cross section along the line a-a and a
cross section along the line b-b on the right side. Hereinafter, the
holograms in accordance with the phase patterns in FIGS. 7(A) to 7(D) are
respectively referred to as holograms A to D.

[0090]Next, in accordance with the phase pattern of the circular pattern
101 with a phase modulation degree of π/2 and a diameter of 32 pixels,
which is displayed in the display region 100 in FIG. 7(A), the phase of
light was modulated to generate sample light, and the holograms A to D
were each irradiated with the sample light. FIG. 8 shows the results of
detecting reproduced light reproduced from the holograms A to D, where
the vertical axis indicates a correlation value (the intensity of
reproduced light) in terms of arbitrary unit, normalized by a correlation
value of autocorrelation, and the horizontal axis indicates the
respective holograms A to D. The hologram A recorded with the use of the
object light in accordance with the phase pattern in FIG. 7(A) is
coincident with the sample light, and thus has autocorrelation. The
hologram B recorded in accordance with the phase pattern with the
circular pattern 102 displayed with a phase modulation degree of π and
a diameter of 10 pixels in FIG. 7(B), has cross-correlation with the
phase pattern in FIG. 7(A) corresponding to the sample light, but has a
higher correlation value of 63 as compared with the holograms C and D
because of a small difference in phase pattern. The holograms C and D
each have correlation values 48 and 31, and it can be thus confirmed that
the correlation value is decreased with increase in the difference (the
number of circular patterns 102 with a phase modulation degree of π
and a diameter of 10 pixels) with respect to the phase pattern in FIG.
7(A) corresponding to the sample light. This suggests that it is possible
to identify the number of cells, the presence or absence of a cell
nucleus, etc. in the phase object identification device according to the
present invention.

EXAMPLE 2

[0091]The device 80 in FIG. 6 was used to demonstrate the possibility of
identifying phase objects in response to change in phase. The device in
this example had the same conditions as in Example 1. First, the phase
was changed by π/4 from 0 to 2π for all of the pixels in the
display region of 32×32 pixels of the phase spatial light modulator
84 to generate object light for each pixel, and record nine holograms by
interference between the object light and the reference light. More
specifically, the object light in accordance with the phase patterns in
which the phase was set to 0, π/4, π/2, π/4, π, 5π/4,
3π/2, 7π/4, and 2π for all of the pixels in the display region
was used to record holograms 0, π/4, π/2, 3π/4, π, 5π/4,
3π/2, 7π/4, and 2π.

[0092]These nine holograms were irradiated with sample light generated in
accordance with a phase pattern in which the phase was set to 0 for all
of the pixels in the display region. FIG. 9 shows the results of
detecting reproduced light reproduced from the holograms 0, π/4,
π/2, 3π/4, π, 5π/4, 3π/2, 7π/4, and 2π, where the
vertical axis indicates a correlation value (the intensity of reproduced
light) in terms of arbitrary unit, normalized by a correlation value of
autocorrelation, and the horizontal axis indicates the respective
holograms. The hologram 0 and the hologram 2π recorded with the use of
the object light in accordance with the phase patterns with the phase of
0 for all of the pixels is coincident with the sample light, and thus has
autocorrelation. The correlation value is larger when the hologram of
interest is closer to the hologram 0 and the hologram 2π, and smaller
when the hologram of interest is further from the hologram 0 and the
hologram 2π, and the hologram π has the smallest correlation value.
According to Example 2, the phase difference between the phase object to
be identified and the known phase object can be identified as the
intensity of the reproduced light. Furthermore, it is suggested that the
application of Example 2 allows vibrations of cells, expansions of cells,
and dynamic changes in phase to be observed or identified.